1. Technical Field
The present invention relates to bismaleimide resin, and more particularly to a modified with an aromatic diamine containing fluoro substituents (hereinafter referred to as the fluorine-containing modified bismaleimide resin).
2. Description of Related Art
Bismaleimide (BMI) is a dual-function compound with maleimide as the end group and is a thermosetting resin reacting with various compounds. Bismaleimide is structurally compact and firm as well as has excellent physical and dielectric properties, such as high thermal stability, good mechanical properties, high glass transition temperature (Tg) and great toughness, making it a good material for heat resistant circuit boards, copper clad laminates (CCL) or resin coated copper (RCC).
However, traditional bismaleimide resin is relatively less tenacious and thus brittle. In addition, it is less soluble in solvents, and has high dielectric constant Dk and high water absorption. Also, its processability is poor.
For improving the traditional bismaleimide resin in these aspects, modification is necessary. For example, both U.S. Pat. Nos. 5,071,947 and 5,025,079 propose modifying bismaleimide resin with diamine monomer. The modified bismaleimide resin made by polymerizing bismaleimide and aromatic diamine does have significantly improved tenacity and solvent solubility. Nevertheless, since according to these known approaches aromatic diamine used for modification does not contain any fluoro substituents, the products as modified bismaleimide resin still has its dielectric constant Dk and water absorption relatively high.